Separable drill bit



June 10, 1947. j J. B.YBAKER, JR 2,421,826

SEPARABLE DRILL BIT Filed April 9, 1945 a I l \6 Patented June 10, 1947UNITED STATES PATIENT OFFICE SEPARABLE DRILL BIT John 13. Baker, Jr.,Canton, Ohio Application April 9, 1945, Serial No. 587,263

2 Claims. 1 My invention relates to separable drill bits, particularlyadapted for rock drilling and of the type wherein the bit body has acentral bore at the end remote from the cutting edges adapted to receivea projecting pin on a drill rod, the end of the bit body having a flatface adapted to seat against 'a shoulder on the drill rod at the base ofsaid pin. Bits and drill rods of this general type are commonly providedwith inter-engaging threads or with cams, keys or other special securingdevices. All of such prior constructions involve danger of breakage ofweak parts and danger of binding of the parts to such an extent thatseparation is prevented.

The present invention is concerned with overcoming disadvantages, suchas those above mentioned, and its principal object is a connectionbetween the bit and drill rod, which is very strong, which is simple tomanufacture, which eliminates separate fastening devices, which willprovide automatic positive inter-engagement of the parts and which, atthe same time, will permit easy separation of the parts, when desired,without creating any risk of accidental disengagement of the parts.

The invention consists principally in making the projecting pin or thedrill rod and the bore of the bit body of constant circular sectionthroughout, but with an endwise or longitudinal curvature of relativelylarge radius. The invention further consists in the separable drill bitand in the parts and combinations of parts hereinafter described andclaimed.

In the accompanying drawing,

Fig. 1 is a side elevation of a separable drill bit and rod embodying myinvention, the rear portion of the bit body being shown in longitudinalsection to illustrate the endwise curvature of the drill rod pin and thebore of the bit body; and

Fi 2 is a cross-sectional view on the line 2-2 in Fig. 1.

The drawing illustrates a drill bit comprising a body I having anydesired number and arrangement of cutting or drilling edges 2 and adrill rod 3 to which the bit body I is separably secured. The rear orskirt portion 4 01 the bit body has a central bore 5 extendinglongitudinally of the bodyandthedrillrodihasaprojectingpinfi extendinginto said bore. The rear or skirt portion or the bit body has a. flatface I that abuts against a flat shoulder 8 on the drill rod 3 at thebase of said pin 9.

The pin 8 and the bore 5 of the bit body are of constant circularsection throughout, the diameter of the pin 9 being such as to fltsnugly within said bore and the pin being shorter than the bore, so asto avoid contact between the end of the pin and the bottom of said bore.

The pin 6 and bore 5 are both curved endwise or longitudinally on alarge radiu oi curvature, the center 9 of such curvature being locatedforwardly of the plane of the drill rod shoulder 8.

Obviously, the bit may be slipped over the pin 6 by alining the twocurvatures and then swinging the bit I and moving it endwise over thepin until the rear face 1 of the bit skirt is seated against theshoulder 8 on the drill rod. Relative rotation of the drill rod 3 andbit I will obviously lock the parts together. The location of the centerof curvature of the pin and bore forwardly of the shoulder 8 on thedrill rod eliminates any tendency of one side of the bit to pull awayfrom the drill rod shoulder during locking movement. The parts may bedisassembled by reversing the assembling steps.

The above described construction has important advantages besides itsobvious simplicity and strength or construction and ease of manufacture.Locking of the parts is automatic regardless of the direction ofrotation of the drill rod. Special fastening devices are dispensed with.Accidental separation of the parts in the drill hole is preventedbecause of the impossibility of tilting the bit on of the stud until thebit and drill rod are removed from the drill hole. Separation of theparts when removed from the drill hole is quite simple.

What I claim is:

1. A separable drill bit construction comprising a hollow bit having abore for receiving the end of a drill rod, a rod having a shoulderagainst which the end oi. said bit abuts and a projecting pin extendinginto said bore, said bore and said pin being of constant circularsection throughout their length and being curved endwise on an arc oflong radius, the center of said are being located forwardly oi the planeof said shoulder.

2. A drill rod for a separable bit having a shoulder against which theend of said bit abuts and a projecting pin of circular sectionthroughout its length and curved endwise on an arc oi. 1on8 radius, thecenter oi said are being located forwardly of the plane of saidshoulder.

I JOHN B. BAKER, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS -Numbe r\ Name Date 534,152 Heinkel et a1 Feb. 12,1895 2,122,244 Brown June 28, 1938 1,998,759 Horton et al. Apr. 23, 1935

